A fairly recently marketed new type of panel, for example, has a sandwich structure with only the two outer layers made of wood (possibly with a treated-paper veneered surface), and with a honeycomb cardboard or foam material inner layer, and weighs about a fifth of a conventional panel.
Panels of this sort have the definite advantage of being much lighter than currently used chipboard or MDF (Medium Density Fibreboard) panels, and employ less wood. On the other hand, using current techniques, they fail to provide for effective adhesion of the edging material, for lack of a compact layer, between the outer layers, to which to attach the joins of the edging material at the corners.
Another drawback of this new type of panel is the need for a new type of hardware fittings to ensure furniture of strong make, and which appears to be difficult to achieve on account of the extremely weak nature of the inner layer of the sandwich panel.
A panel of this sort is described in European Patent EP-B1-1 563 970 B1 (IMA Klessmann GmbH).
The panel described in the above patent only partly solves the edging problem, on account of the difficulty in grooving and inserting the reinforcing strips in the remaining two sides, once the first two have been grooved and the reinforcing strips inserted.
That is, since grooving tools are necessarily circular, and not being possible to run out from the ends of the first two sides already edged, tool entry and exit along the second two sides must be programmed accordingly, thus resulting in incomplete grooves along these sides; and the inside end portions of the reinforcing strips must also be rounded off to insert them inside the ends of the incomplete grooves in the second two sides.
Moreover, the sides of the panel must be machined accurately to ensure the reinforcing strip is aligned perfectly with the outer surfaces of the outer layers of the panel.
And the thickness of the reinforcing strip must be perfectly calibrated to match the groove formed in the side.
Neither does the EP-B1-1 563 970 B1 (IMA Klessmann GmbH) solution solve the hardware fitting (hinge, etc.) problem, on account of the part of the panel to which the hardware fitting is fitted being hollow or at any rate weakened by the poor consistency of the inner layer of the panel.
To solve this problem, some makers insert inside the edge of the sandwich panel a long strip of wood, which must be cut to size to match the length of the edge. This results in excessive use of wood, on account of the strip also being fitted to parts of the edge where it is not needed, and the difference between the standard length of the wood strips and the actual length of the panel results in considerable waste.